Japanese Patent Application No. 2000-280845 is known as an example of an airbag device installed to a front seat of a vehicle such as an automobile. In Japanese Patent Application No. 2000-280845, an airbag of an assist airbag device is formed in an outer dimension which enables an occupant sitting on a front window seat and an occupant sitting on a center seat to be restrained. A partition is provided in the airbag to divide the airbag into an airbag for a center seat occupant which is deployed in front of the center seat and an airbag for a front window seat occupant which is deployed in front of the front window seat. An inflator is connected to the airbag for a center seat occupant. A communication hole which allows communication between the inside of the airbag for a center seat occupant and the inside of the airbag for a front window seat occupant is opened on the partition and an exhaust hole which communicates with the outside is opened in a side portion of the airbag for a front window seat occupant.
In recent years, regarding occupant protection by a vehicular airbag device, measures against diagonal collisions which is one of the collision modes of vehicles are being considered. A diagonal collision is an intermediate collision mode between a head-on collision and a side collision. In a diagonal collision, an end part in a vehicle width direction in a front part of a vehicle in a longitudinal direction (a front right corner or a front left corner) is the point of collision and the vehicle turns around this collision point. In a head-on collision, the body of an occupant moves forward in the vehicle longitudinal direction from a seat. In a side collision, the body of an occupant moves rightward or leftward in the vehicle width direction. In the case of a diagonal collision in which a turning force acts on the vehicle, an occupant is subjected to forces in both the vehicle longitudinal direction and the vehicle width direction. Therefore, an occupant moves diagonally forward in the vehicle longitudinal direction from a seat. In addition to a force that causes a diagonally-forward movement, the body of the occupant is also subjected to a rotating force in a similar manner to the vehicle subjected to a turning force. Therefore, the body of the occupant rotates while tilting diagonally with respect to the vehicle longitudinal direction. In doing so, the head of the occupant also rotates left and right with the neck as an axis.
As indicated by a dotted line in FIG. 70 appended to this specification, a conventional vehicular front seat airbag #a is configured so as to deploy and expand rearward in a vehicle longitudinal direction toward an occupant 101 sitting on a front seat of a vehicle from an opening 104 of an instrument panel 102. Conventionally, an outer shape of the airbag #a when fully deployed and expanded as viewed downward from above the vehicle is a triangular shape or a fan-like shape in which an occupant restraining surface #b that catches and restrains the occupant 101 is wide in a vehicle width direction and a front end #c in the vehicle longitudinal direction on the side of the opening 104 tapers off and is narrow in the vehicle width direction.
In the case of the conventional vehicular front seat airbag #a, even when attempting to restrain the occupant 101 moving diagonally forward in the vehicle longitudinal direction due to a diagonal collision with the occupant restraining surface #b, the airbag #a ends up rotating around the front end #c in the vehicle longitudinal direction together with the body of the occupant 101 which rotates so as to tilt diagonally while moving. Therefore, the body of the occupant 101 escapes to a side of the airbag #a to create a problem in that the body of the occupant 101 cannot be appropriately restrained by the occupant restraining surface #b or, in other words, there is no surface for restraining the occupant 101. In addition, since the body of the occupant 101 cannot be appropriately restrained, there is also a problem that a rotation of the head 101a of the occupant 101 around the neck cannot be suppressed and, accordingly, a head obstruction value of the occupant 101 is also high.
The present invention has been devised in consideration of the conventional problems described above and an object thereof is to provide a vehicular airbag device capable of improving reduction of an occupant obstruction value during a diagonal collision.